#autoload

autoload add-zsh-hook
zmodload zsh/system || exit 1

typeset -g hlxtout hlxtin stderr oPS4="$PS4"
coproc highlight -S sh -O xterm256
exec {hlxtout}<&p
exec {hlxtin}>&p
exec {stderr}>&2

# We don't want the commands that are managing highlighting to appear
# in the trace output, so create them "sticky" with xtrace disabled
emulate zsh +x -c '
  hlxt_precmd() {
    local xtrace xt xc=0
    # Unfortunately this has to use a one-second timeout because
    # "highlight" does not always write quickly enough.
    #
    # Manual says combining sysread -o with a param is valid, but
    # that does not work; neither output nor parameter is written.
    # while sysread -t 1 -i $hlxtout -c xc -o $stderr xtrace
    while sysread -t 1 -i $hlxtout -c xc xtrace
    do
      [[ -n $xtrace ]] && print -n -u $stderr -r -- "${xt::=$xtrace}"
    done
    # Need to handle error?  (( $? < 4 && xc )) && [[ -n $xtrace ]]
    [[ -z $xt || $xt == *$'"'\\n'"' ]] || echo
  }
  hlxt() {
    setopt localoptions localtraps
    case $1 in
    (on|)
      add-zsh-hook precmd hlxt_precmd || exit 1
      PS4=
      exec 2>&$hlxtin
      # Bypass local scope restore of xtrace
      trap "setopt xtrace" EXIT
    ;;
    (off)
      exec 2>&$stderr
      PS4="$oPS4"
      add-zsh-hook -d precmd hlxt_precmd
      trap "unsetopt xtrace" EXIT
      # Flush leftovers
      local stderr
      hlxt_precmd {stderr}>&/dev/null
    ;;
    (*) add-zsh-hook -L
  esac
  }
'